1. Field of the Invention
The present invention relates to a sleeping bag having a zip fastener of the zipper or slide fastener type extending from the foot end up to the head end thereof. More specifically, the invention pertains to sleeping bags of practically any kind of design; however, especially to down-filled sleeping bags which are of the conventional rectangular shape as well as of the so-called mummy configuration.
A zip or slide fastener, frequently referred to as a zipper which renders it easier for a person to slip into the sleeping bag, is critically with regard to its ease of manipulation by the user and its disadvantage as an undesirable cold-transmitting bridge. Heretofore, sleeping bags have been constructed with either a central slide or zip fastener or alternatively, with a zip fastener opening along the side of the bag, with the zip fastener extending either continuously from the foot end to the head end, or also being formed as a shorter zip fastener extending only over an upper portion of the length of the sleeping bag.
2. Discussion of the Prior Art
Sleeping bags which are equipped with a short central zip fastener can be more easily manufactured and insulated. The operation of a zip fastener which is located in a region on the chest is easier to handle than one situated at the side near the region of the shoulder. A disadvantage encountered with short central zip fasteners or even short side zip fasteners resides in that it is not possible to vent or air out the sleeping bag in the region of the foot end through a partial opening thereof. It is also not possible to employ such a sleeping bag as a cover or blanket since it cannot be opened completely.
Although slide or zip fasteners which extend continuously from the foot end to the head end of the sleeping bag form a larger cold-transmitting bridge this can, however, be controlled to a great extent through the provision of an appropriate covering or flap; while nevertheless rendering considerably easier the entry of the user, facilitating the airing out of the foot end; and in combination with a zip fastener which extends about in the region of the foot end, to convert the bag into a cover or blanket. Sleeping bags of this kind can also be joined together by the through-extending zip fastener in order to produce a double sleeping bag.
Inasmuch as sleeping bags with full-length or continuous side zip fasteners can be employed in a greater variety of ways they have been more successfully commercialized in the market. However, a zip fastener which is situated at the side in the shoulder region at the head end of the bag is more difficult to manipulate by the user and creates the problem of providing insulation in precisely the important shoulder region of the sleeping bag.